Many electronic circuits require, for their proper operation, a highly stable voltage reference source that is insensitive to variables such as temperature and the variations of the supply voltage level. Bandgap reference voltage sources with such stable output voltages may be constructed based on the physics of semiconductor p-n junctions. Bandgap reference voltage sources must be carefully set, or calibrated, in order to provide such stable voltages of known value. The calibration is highly sensitive to variations in the fabrication process, and must therefore be performed on each instance of the bandgap reference circuit for the highest accuracy and stability. To do this during manufacturing, however, is costly and excessively time-consuming.